The invention is based on a clamp for balancing.
In rotating bodies, the centrifugal forces relative to the axis of rotation balance one another out, if the masses of the rotating body are balanced. Unbalanced masses, resulting for instance from production variations, engender revolving, radially acting centrifugal forces that cyclically put a load on the bearing in alternating directions. Since because of the elasticity of the material and the intrinsic mass, each component is a spring-mass system capable of vibration, it can be induced to vibrate by cyclical forces; excitations in the range of the natural frequency can be especially problematic and can lead to permanent damage to the bearings and other components. For this reason, especially in bodies that rotate at high speed, such as impellers of fans, imbalances that exist after assembly are ascertained and compensated for by balancing weights.
To compensate for an imbalance, in radial fans so-called balancing clamps are secured to the relatively thin impeller vanes. Various clamps are known, which are made from sheet spring steel or round wire and as a rule are inserted from outside onto the impeller vanes of the fan. The clamps are designed structurally such that they completely surround the impeller vanes or have insert detent zigzags with which they mesh in clawlike fashion. However, for installing the claws with insert detent zigzags, considerable force must be expended. Furthermore, the clamps can catch on one another. They then have to be separated into individual clamps before assembly, which is complicated, and can therefore be incorporated only poorly into an automatic process. Finally, there is the risk that many clamps, under the influence of external forces during operation, will change their position or become loose, so that imbalances that lead to problems arise once again. Then the component has to be balanced all over again.
According to the invention, a clamp for balancing an imbalance has a U-shaped cross-sectional profile with at least one tip formed onto a leg; the tip protrudes into the interior of the U-shaped cross-sectional profile and extends at an incline toward the connecting part of the legs. The clamp can be mounted axially or radially by being bent open elastically widely enough that the legs with the formed-on tip can be slipped over the body having the thin-walled part, such as an impeller vane. The prestressing of the clamp presses the tip against the impeller vane, and the tip digs into the surface of the impeller vane slightly. If forces such as centrifugal forces or impact forces act on the clamp outward, the legs of the clamp are increasingly spread apart by the tip, so that the contact pressure of the tip is, increased and its seat is solidified. Thus the clamp cannot be removed without a special tool, nor can it change its position, once assumed, unintentionally.
Expediently, a plurality of tips are disposed axially offset from one another on one leg and alternate with tips on the other leg. In the unmounted state, the tips of one leg are located in the interstices between the tips of the other leg, so that for a long spring path for the prestressing, the clamps require little space in the dismantled state. In the mounted state, the tips dig from both sides into the thin-walled component, that is, the impeller vane, and thus axially and radially reinforce the retention created by the prestressing.
On a body that is to be balanced, such as an impeller vane, the clamps can be mounted axially and/or radially, depending on the design of the body. They are mounted in such a way that the connecting part and thus also the tips point toward the outer circumference of the impeller vane. The centrifugal force increases the angle of inclination of the tips to the legs, and as a result the clamp is resiliently bent open and thus reinforces the contact pressure against the impeller vane. A correspondingly reinforced resistance is also presented to axially acting forces, by means of a triangular shape of the tips. The clamp is thus stably fixed in its position and can accordingly not be removed from the fan without aids. This is important for the further use until the system is completed, since a worn or displaced clamp would necessitate later work in the form of rebalancing.
To enable mounting the clamp well, the ratio between the retaining force and the slip-on force is modified by providing that the design of the tips and their inclination to the legs are adapted to installation conditions.
The shape of the clamp of the invention selected such that in the unmounted state, the tips protrude into the U-shaped interior and optionally dip into the respective opposed contour. Axial indentations are provided for this purpose in the associated legs. The indentations protrude vertically and horizontally past the tips, so that the tips are always covered by adjacent parts of the outer contour of the clamp. Advantageously, the peripheral region of a leg is bent outward, in order to cover a tip protruding through its indentation if applicable. This prevents loose clamps from catching on one another before being mounted. Moreover, they can easily be separated and are therefore especially well suited to automatic production processes. To enable automatic separation and alignment of the clamps in a simple way, it is expedient that the legs are of different lengths.
In a feature of the invention, the clamps have recesses. By means of the size, shape and position of the recesses or the contour of the clamps, many variants of similar clamps with different masses and mass distributions can be made. As a result, the clamps can be used for many applications, such as for fans of different sizes, and so forth.